Car Audio (in dash LCD help)

I just installed my new head unit, now it's an indash lcd screen and they make you have a cable running to your parking break so the monitor will turn on.(it worked for a 'lil bit, so i know it's not a mechanical failure) The guy i bought this from (ebay) said that if i hooked this wire into my ground it would work while the car was moving, Anyone else have something similar to this that could clue me in a bit more because that didn't work and i can't seem to google this.

all its looking for is the precence for an electrical current or mabye no current.. try hooking it into your radio fuse so it powers on when your radio does, or ground it and it whould work.

well it's currently in the crip with the Ground...i thought hooking it into a live wire would make more sense, gonna try that next, but figured i'd see if anyone else has done an install like this b4 possibly shorting something out

if you are worried about shorting it out use an inline fuse.. that will help protect it.